I'm doing a fresh install on a machine with a GTX670 GPU in it. I've read about the proprietary drivers from nvidia, would those be my best bet for performance with this GPU or a set of drivers from within the update/install functionality of mint?

You can download driver from nvidia.com and manually install it or add repository and get drivers through apt-get. I followed this how-to: http://www.itworld.com/software/289579/install-nvidia-driver-30432-linux-mint-13-or-ubuntu-12041210. After that you will be able to change drivers through: Menu->Preferences->Software Sources->Additional Drivers Tab. I think it is best way to add driver because thanks to that I have single repository to manage software. I prefer prioprietary driver instead open source because I had problems with memory allocation on open source. I use 310 experimental with my GTX 660.